usb: dwc3: gadget: introduce cancelled_list

commit d5443bbf5fc8f8389cce146b1fc2987cdd229d12 upstream

This list will host cancelled requests who still have TRBs being
processed.

Cc: Fei Yang <fei.yang@intel.com>
Cc: Sam Protsenko <semen.protsenko@linaro.org>
Cc: Felipe Balbi <balbi@kernel.org>
Cc: linux-usb@vger.kernel.org
Cc: stable@vger.kernel.org # 4.19.y
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
(cherry picked from commit d5443bbf5fc8f8389cce146b1fc2987cdd229d12)
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>